The present invention relates to an airbag which expands and deploys by gas introduced therein, an airbag folding method, and an airbag device.
It has been used an airbag device mounted, for example, to a steering wheel of a motor vehicle. The airbag device comprises an airbag, an inflator for supplying gas to the airbag, and a cover for covering the airbag accommodated in the folded state. Various airbag folding methods have been proposed to achieve a reduction in manufacturing cost and an enhancement in deployment characteristic.
In order to enhance the deployment characteristic of the airbag mounted to the steering wheel, the airbag is obtained, for example, by superimposing circular base cloths one upon another, wherein the airbag includes an upper deployment portion corresponding to the head of an occupant or passenger and a lower deployment portion. With such airbag, a deployment section of the folded upper deployment portion located on the occupant side from side to side is folded, and then the lower deployment portion is folded on the occupant side of the deployment section. With this structure, when the airbag device is actuated, the lower deployment portion starts to expand and deploy toward a space corresponding to the occupant s chest and abdomen at the initial stage of airbag deployment, allowing the airbag to largely deploy toward the space before the occupant inclines forward. After the lower deployment portion deploys, the upper deployment portion and the like expand and deploy subsequently to restrain the occupant s head.
In this respect, in connection with the positional relationship between the automotive seat and the steering wheel and the like, the airbag device may be required to quickly deploy toward the occupant s head.
Moreover, in order to suitably restrain the occupant even if he/she is seated close to the steering wheel, the cover of the airbag device mounted to the steering wheel may comprise a lower lid rotating downward and an upper lid rotating upward, wherein the upper lid is divided into right and left portions. With this structure, even if the occupant is seated close to the steering wheel, the right and left portions of the upper lid deploy compactly without interfering with the occupants face, and rotate frontward of a rim without interfering therewith. Thus, when the occupant is seated close to the steering wheel, the airbag expanding from the cover deploys frontward from the inside of a rim portion of the airbag to reduce the pressure to be applied to the occupant, allowing appropriate restraint of the occupant.
In this respect, the airbag device is required to provide more appropriate and favorable deployment characteristic.